Polyimide curing process and improved thermal ink jet printhead prepared thereby

Abstract

Disclosed is a process which comprises reacting a polyimide precursor with borane. Also disclosed is a thermal ink jet printhead containing a layer comprising the product of this reaction.

Claims

1. An ink jet printhead which comprises (i) an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles, (ii) a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes formed thereon, and (iii) a thick film layer deposited on the surface of the lower substrate and over the heating elements and addressing electrodes and patterned to form recesses therethrough to expose the heating elements and terminal ends of the addressing electrodes, said thick film layer comprising the reaction product of a polyimide precursor with borane, the upper and lower substrates being aligned, mated, and bonded together to form the printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles.

2. A printhead according to claim 1 wherein the polyimide precursor is of the formula ##STR12## wherein A is --O--, --C(CH.sub.3).sub.2 --, --S--, ##STR13## wherein z is an integer of from 1 to about 20, or mixtures thereof, and wherein n is an integer representing the number of repeating monomer units, or ##STR14## wherein B is --O--, --C(CH.sub.3).sub.2 --, --S--, ##STR15## wherein z is an integer of from 1 to about 20, or mixtures thereof, wherein R is hydrogen, an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, an arylalkyl group, a substituted arylalkyl group, an acrylate group, a methacrylate group, or a mixture thereof, and wherein n is an integer representing the number of repeating monomer units, or mixtures thereof.

3. A printhead according to claim 2 wherein n is an integer of from about 5 to about 65.

4. A printhead according to claim 2 wherein n is an integer of from about 10 to about 15.

5. A printhead according to claim 1 wherein the reaction generates a material comprising a polymer of the formula ##STR16## wherein A is --O--, --C(CH.sub.3).sub.2 --, --S--, ##STR17## wherein z is an integer of from 1 to about 20, or mixtures thereof, and wherein n is an integer representing the number of repeating monomer units.

6. A printhead according to claim 1 wherein the reaction generates a material comprising a polymer of the formula ##STR18## wherein B is --O--, --C(CH.sub.3).sub.2 --, --S--, ##STR19## wherein z is an integer of from 1 to about 20, or mixtures thereof, and wherein n is an integer representing the number of repeating monomer units.

7. A process for preparing an ink jet printhead which comprises the steps of:

(a) providing a photopatternable polyimide precursor polymer;

(b) depositing a thick film layer comprising the photopatternable polymer onto a lower substrate in which one surface thereof has an array of heating elements and addressing electrodes having terminal ends formed thereon, said photopatternable polymer being deposited onto the surface having the heating elements and addressing electrodes thereon;

(c) exposing the thick film layer to actinic radiation in an imagewise pattern, wherein the unexposed areas correspond to areas of the lower substrate having thereon the heating elements and the terminal ends of the addressing electrodes;

(d) removing the photopatternable polymer from the unexposed areas, thereby forming recesses in the thick film layer, said recesses exposing the heating elements and the terminal ends of the addressing electrodes;

(e) reacting the photopatternable polymer in the exposed areas with borane;

(f) providing an upper substrate with a set of parallel grooves for subsequent use as ink channels and a recess for subsequent use as a manifold, the grooves being open at one end for serving as droplet emitting nozzles; and

(g) aligning, mating, and bonding the upper and lower substrates together to form a printhead with the grooves in the upper substrate being aligned with the heating elements in the lower substrate to form droplet emitting nozzles.

8. A process according to claim 7 wherein the borane is in gas form.

9. A process according to claim 7 wherein the borane is present in an organic solvent.

10. A process according to claim 9 wherein the organic solvent is selected from the group consisting of tetrahydrofuran, dimethyl sulfide, pyridine, methylamine, and mixtures thereof.

11. A process according to claim 7 wherein the reaction takes place at a temperature of from about 0.degree. to about 100.degree. C.

12. A process according to claim 7 wherein the reaction takes place at a temperature of from about 15.degree. to about 35.degree. C.

13. A process according to claim 7 wherein the polyimide precursor is a polyamic acid or polyamic ester.

14. A process according to claim 7 wherein the polyimide precursor is of the formula ##STR20## wherein A is --O--, --C(CH.sub.3).sub.2 --, --S-- ##STR21## wherein z is an integer of from 1 to about 20, or mixtures thereof, and wherein n is an integer representing the number of repeating monomer units, or ##STR22## wherein B is --O--, --C(CH.sub.3).sub.2 --, --S--, ##STR23## wherein z is an integer of from 1 to about 20, or mixtures thereof, wherein R is hydrogen, an alkyl group, a substituted alkyl group, an aryl group, a substituted aryl group, an arylalkyl group, a substituted arylalkyl group, an acrylate group, a methacrylate group, or a mixture thereof, and wherein n is an integer representing the number of repeating monomer units, or mixtures thereof.

15. A process according to claim 14 wherein n is an integer of from about 5 to about 65.

16. A process according to claim 14 wherein n is an integer of from about 10 to about 15.

17. A process according to claim 7 wherein the reaction generates a material comprising a polymer of the formula ##STR24## wherein A is --O--, --C(CH.sub.3).sub.2 --, --S--, ##STR25## wherein z is an integer of from 1 to about 20, or mixtures thereof, and wherein n is an integer representing the number of repeating monomer units.

18. A process according to claim 7 wherein the reaction generates a material comprising a polymer of the formula ##STR26## wherein B is --O--, --C(CH.sub.3).sub.2 --, --S--, ##STR27## wherein z is an integer of from 1 to about 20, or mixtures thereof, and wherein n is an integer representing the number of repeating monomer units.